In the case of applying an electron-emitting device using an electron-emitting film to an image display apparatus using phosphors, the electron-emitting device must produce an emission current sufficient for irradiating the phosphors with sufficient luminance. In addition, the size of the electron beam irradiated on the phosphors must be smaller as a higher resolution (definition) of the image display apparatus (display) is desired. Moreover, it is important that the apparatus itself is easily manufactured.
A cold cathode electron source, which is one type of the electron-emitting device, includes a field emission type (hereinafter referred to as “FE type”), a surface conduction electron-emitting device, or the like.
For the FE type, a Spindt type is highly efficient and expected. However, an electron-emitting device of the Spindt type has a complicated manufacturing process and, moreover, tends to disperse the electron beam it produces. Thus, it is necessary to arrange a focusing electrode above an electron-emitting part in order to prevent spreading of the electron beam.
On the other hand, examples of an electron-emitting device with which the spot size of an electron beam does not increase so much as with the Spindt type, are disclosed in, for example, JP 08-096703 A, JP 8-096704 A, JP 8-264109 A, and the like. Those electron-emitting devices cause electrons to be emitted from a flat thin film (electron-emitting film) arranged in a hole thereof. Thus, a relatively flat equipotential surface is formed on the electron-emitting film and widening of the electron beam is reduced, while the electron-emitting devices can be manufactured relatively easily. In addition, reduction of a drive voltage necessary for electron emission can be realized by using a material of a low work function as a substance forming the electron-emitting film. Moreover, the electron emission is performed in a planar shape (in the Spindt type, it is performed in a dot shape), so that concentration of electric fields can be relaxed. Thus, long life of the electron-emitting device can be realized. A carbon based electron-emitting film has been proposed as such a flat electron-emitting film. An electron-emitting device using a carbon based film is disclosed in, for example, “A Study of Electron Field Eemission as a Function of Film Thickness from Amorphous Carbon Films”, R. D. Forrest et al., Applied Physics Letters, Volume 73, Number 25, 1988, P3784, and the like. Further, examples of carbon films having various metals added therein are disclosed in, for example, “Electron Field Emission from Ti-Containing Tetrahedral Amorphous Carbon Films Deposited by Filtered Cathodic Vacuum Arc”, X. Z. Ding et al., Journal of Applied Physics, Volume 88, Number 11, 2000, P6842; “Field Emission from Cobalt-Containing Amorphous Carbon Composite Films Heat-Treated in an Acetylene Ambient”, Y. J. Li et al., Applied Physics Letters, Volume 77, Number 13, 2000, p2021; “Low-Macroscopic-Field Electron Emission from Carbon Films and Other Electrically Nanostructured Heterogeneous Materials: Hypotheses About Emission Mechanism”, Richard G. Forbes, Solid-State Electronics 45 (2001) pp. 779-808; “Field Emission from Metal-Containing Amorphous carbon Composite Films”, S. P. Lau et al., Diamond Related Materials, 10 (2001) pp. 1727-1731; JP 2001-006523 A; JP 2001-202870 A; and the like.
In addition, electron-emitting films using a conductive material and an insulating material are studied in various ways. Such electron-emitting films are disclosed in, for example, “Enhanced Cold-Cathode Emission Using Composite Resin-carbon Ccoatings”, S. Bajic and R. v. Latham., J. Phys. D: Appl. Phys., 21 (1988) pp. 200-204; “Field Emitting Inks for Consumer-Priced Broad-Area Flat-Panel Displays”, A. P. Burden et al., J. Vac. Sci. Technol. B, 18 (2), March/April (2000) pp. 900-904; Japanese Utility Model Application Laid-open No. 04-131846; and the like. Moreover, there are reports on electron-emitting films such as one in which a conductive material is added in pores of an insulating material as disclosed in JP 2001-101966 or one in which, in a cermet of ceramics and metal, electrons are injected into an insulating layer from the metal to emit the electrons as disclosed in U.S. Pat. No. 4,663,559.